1. Field of the Invention
The present invention relates to an automotive vehicle steering control device, which modifies a target steering quantity depending on a manual steering force by the driver""s operation, to conduct the steering based on the driver""s intention even under an automatic steering control.
2. Description of the Related Art
Various attempts have been made to superimpose the automatic steering operation and the driver""s steering operation to improve a so-called automatic vehicle steering system which allows at least some part of the steering operation to be automated during running of the automotive vehicle.
Japanese Patent Application Laid-open No. 9-128699 discloses an automotive vehicle steering angle correcting device, which is provided with a drive device between a steering wheel grip portion that is operated by a driver and a directing device, and which generates such a drive output as to obtain a steering quantity required for maintaining a vehicle running lane, thereby enabling the driver""s over-ride under the automatic steering control.
Japanese Patent Application Laid-open No. 9-221054 discloses an automotive vehicle steering device in which an actuator for driving a directing device to follow the vehicle running lane is provided to conduct the lane maintaining control. The steering device serves to increase or decrease a torque generated between the directing device and the steering operated by a driver depending on a difference between an angle of the directing device and an angle of the steering operated by the driver, inform the driver of the angular difference between the target steering angle and the angle of the steering operated by the driver, and provide a function to adjust the running course in the lane depending on the difference. This permits the driver to conduct the over-ride with a natural feeling.
Japanese Patent Application Laid-open Nos. 9-240502, 9-142327, 6-336170, and so on disclose an automotive vehicle steering device, which detects the driver""s over-ride based on the magnitude of the driver""s steering force, the quantity of change in the steering force, the steering speed and so on, and automatically switch over to the manual driving mode when the driver""s over-ride is conducted during the automatic driving mode.
The automotive vehicle steering devices, which are designed to permit the driver""s over-ride as mentioned above, makes it possible to conduct the emergence escaping operation when a danger is judged by the driver, for instance, when an obstructive object on the lane is found during running. Under the current technology, it is, however, difficult to conduct the emergency escaping operation automatically and surely, and therefore, such a system is desirable where man can drive the automotive vehicle with initiative at least when the emergency escape is conducted.
Further, in a system which permits the driver to switch the driving initiative from the automatic steering to the driver at the time of the emergency escaping operation as mentioned above, the switching of the driving initiative is carried out concurrently when the driver performs the emergency escaping operation. Therefore, it is desirable that the torque applied for the purpose of conducting the automatic steering at the time of the switching of the initiative does not hinder the driver""s operation.
More specifically, it is desirable that means provided to conduct the automatic steering, such as a steering actuator, neither acts in contradiction to the driver""s operation nor adversely affects the driver""s feeling at the time of the emergency escaping operation, for example, abruptly changes the driver""s steering torque, to hinder or erroneously conduct the emergency escaping operation.
In view of this, the automotive vehicle steering angle correcting device disclosed in the Japanese Patent Application Laid-open No. 9-128699 or the automotive vehicle steering device disclosed in Japanese Patent Application Laid-open No. 9-221054 can switch over to the manual steering with the operation torque maintained at the time when the driver carries out the emergency escaping operation. Accordingly, these devices do not adversely affects the driver""s feeling at the time of the emergency escaping operation and do not hinder the emergency escaping operation. That is, these system (the automotive vehicle steering angle correcting device and the automotive vehicle steering device) are desirable forms that take into account such an essential factor that the emergency escaping operation be performed by the driver.
Besides, in general, a power steering device is widely used for an automotive vehicle to reduce the driver""s operation force required to operate a directing device. The power steering drive is designed to actuate the directing device in the driver""s operating direction depending on the driver""s operation torque.
Recently, as the power steering device, a motor-driven power steering device is widely used, which has a torque sensor for detecting the driver""s operation force, an electrically-driven motor for actuating the directing device, and a controller for determining and outputting a driving output and a direction of the electrically-driven motor depending on the driver""s operation force detected by the torque sensor.
The motor-driven power steering device provides sufficient output power enabling a large angle steering (turning the handle with the vehicle not moving), and since the power required to steer and direct the running vehicle is generally smaller than the power required for the large angle steering, it can be used as an actuator of the automatic steering system. Assuming that the automatic steering system is incorporated in the automotive vehicle equipped with the motor-driven power steering device, the common use of the electrically-driven motor and the controller makes it possible to realize the automatic steering system with reduced cost, in comparison to a case where the separate electrically-driven motors and the separate controllers are provided.
However, each of the automotive vehicle steering angle correcting device disclosed in the Japanese Patent Application Laid-open No. 9-128699 and the automotive vehicle steering device disclosed in Japanese Patent Application Laid-open No. 9-221054 is designed such that the driving device is provided between the steering wheel grip portion operated by the driver and the directing device, and therefore, the electrically-driven motor of the power steering device, which directly drives the directing device, can not be used commonly as the driving device. For this reason, even in a case where the automatic steering system is incorporated in the vehicle having the motor-driven power steering device, it is necessary to install a dedicated electrically-driven motor and a dedicated controller, resulting in increased cost.
On the other hand, the systems which switch the driving initiative from the automatic steering to the driver in the case of emergency as disclosed such as in the Japanese Patent Application Laid-open Nos. 9-240502 and 9-142327 are each designed to drive the directing device, and therefore it is possible to commonly use the electrically-driven motor and controller of the motor-driven power steering device and thus realize the automatic steering system with reduced cost.
Although these systems are designed to switch the driving initiative from the automatic steering to the driver in the case of emergency, each of these systems interrupts the automatic steering control at the time of the switching, and therefore inevitably encounters the abrupt change of the operation torque. For these reasons, these systems adversely affect the driver""s feeling at the time of the emergency escaping operation and hinder or erroneously conduct the emergency escaping operation. Accordingly, these devices cannot be considered as desirable system forms that take into account such an essential factor that the emergency escaping operation be performed by the driver.
As discussed above, no automotive vehicle steering control device (automatic steering system) is currently available, which has a drive device commonly used with a power steering device and which does not hinder the emergency escaping operation conducted by a driver.
The present invention was made in order to solve the aforementioned problems. An object of the present invention is to provide an automotive vehicle steering control device which has a drive device commonly used by a power steering device and which does not hinder the emergency escaping operation conducted by a driver.
An automotive vehicle steering control device according to a first aspect of the present invention includes: positional relationship detecting means for detecting a positional relationship between a subject automotive vehicle and an automotive vehicle lane; target steering quantity calculating means for obtaining a first-target steering quantity, required for the automotive vehicle to run along the automotive vehicle lane, based on the positional relationship; manual steering force detecting means for detecting a manual steering force with which a driver operates a steering handle; target steering quantity changing means for outputting a second target steering quantity by changing the first target steering quantity based on the manual steering force thus detected; actual steering quantity detecting means for detecting an actual steering quantity; and automatic steering force calculating means for obtaining an automatic steering force required to make the second target steering quantity and the actual steering quantity coincident with each other.
An automotive vehicle steering control device according to a second aspect of the present invention includes: positional relationship detecting means for detecting a positional relationship between a subject automotive vehicle and an automotive vehicle lane; target steering quantity calculating means for obtaining a target steering quantity, required for the automotive vehicle to run along the automotive vehicle lane, based on the positional relationship; manual steering force detecting means for detecting a manual steering force with which a driver operates a steering handle; actual steering quantity detecting means for detecting an actual steering quantity; automatic steering force calculating means for obtaining an automatic steering force required to make the target steering quantity and the actual steering quantity coincident with each other; and manual steering assisting means for superimposing the manual steering force thus detected and the automatic steering force thus obtained to each other.
An automotive vehicle steering control device according to a third aspect of the present invention, further includes: target steering quantity changing means for outputting a second target steering quantity by changing the target steering quantity based on the manual steering force thus detected, wherein the automatic steering force calculating means obtains the automatic steering force required to make the second target steering quantity and the actual steering quantity coincident with each other.
An automotive vehicle steering control device according to a fourth and a ninth aspects of the present invention, further includes: emergency escaping operation judging means for judging a driver""s emergency escaping motion if the manual steering force detected by the manual steering force detecting means exceeds a threshold value preliminarily set for the manual steering force.
An automotive vehicle steering control device according to a fifth and a tenth aspects of the present invention, further includes: automatic steering force holding means for constantly holding the automatic steering force obtained by the automatic steering force calculating means if a notification indicative of the driver s emergency escaping motion is given from the emergency escaping operation judging means.
An automotive vehicle steering control device according to a sixth aspect of the present invention includes: positional relationship detecting means for detecting a positional relationship between a subject automotive vehicle and an automotive vehicle lane; target steering quantity calculating means for obtaining a first target steering quantity, required for the automotive vehicle to run along the automotive vehicle lane, based on the positional relationship; automotive vehicle speed detecting means for detecting an automotive vehicle speed of the subject automotive vehicle: manual steering force detecting means for detecting a manual steering force with which a driver operates a steering handle; target steering quantity changing means for outputting a second target steering quantity by changing the first target steering quantity based on the automotive Vehicle speed and manual steering force thus detected; actual steering quantity detecting means for detecting an actual steering quantity; automatic steering force calculating means for obtaining an automatic steering force required to make the second target steering quantity and the actual steering quantity coincident with each other; and manual steering assisting means for superimposing the manual steering force thus detected and the automatic steering force thus obtained to each other.
An automotive vehicle steering control device according to a seventh aspect of the present invention, further includes: emergency escaping operation judging means for judging a driver""s emergency escaping motion if the manual steering force detected by the manual steering force detecting means exceeds a threshold value that is set based on either one of the automotive vehicle speed detected by the automotive vehicle speed detecting means and the actual steering quantity detected by the actual steering quantity detecting means.
An automotive vehicle steering control device according to an eighth aspect of the present invention, further includes: automatic steering force gradually decreasing means for gradually decreasing the automatic steering force obtained by the automatic steering force calculating means if a notification indicative of the emergency escaping motion is given from the emergency escaping operation judging means.